Pigment signatures reveal temporal and regional differences in taxonomic phytoplankton composition off the west coast of Ireland

The composition of phytoplankton assemblages in April, 1998 in Galway Bay a nd during a summer phytoplankton bloom occurring southwest of Ireland in Au gust, 1998, was characterized by pigments measured by high-performance liqu id chromatography. Pigment data reflecting phytoplankton assemblages domina ted by diatoms in Galway Bay and dinoflagellates in the southwest of Irelan d were compared to phytoplankton cell counts. Significant relationships wer e found between the fucoxanthin concentrations and the diatom cell numbers (P < 0. 0002 r(2) 0.63) during April, and between fucoxanthin (P < 0.0001 r (2) 0.79), 19'hexanoyloxyfucoxanthin (P < 0.0001 r(2) 0.77) concentrations and Gyrodinium aureolum cell numbers during the summer bloom.